Threads

Question 1

What are the two types of threads?

Answer 1

1. User level
2. Kernel level

Question 2

Which thread executes for a time of only one process?

Answer 2

User level

Question 3

Which thread is managed by runtime library routines linked into each application so that it does not require kernel intervention.

Answer 3

User level

Question 4

What are the advantages of User Level threads?

Answer 4

• Thread operations do not have to cross protection boundary.
• Parameter do not need to be copied.

Question 5

What are the disadvantages of User Level threads?

Answer 5

• Kernel implements a single policy or pays overhead of managing multiple policies.
• User-level threads that issue blocking calls to the kernel will block an entire process.

Question 6

Which thread avoids the system integrations problems, directly scheduling each application’s threads onto physical process.

Answer 6

Kernel level

Question 7

What are the advantages of Kernel Level threads?

Answer 7

• “Correct” kernel level support.
• Can take advantage of multiple CPUs.

Question 8

What are the disadvantages of Kernel Level threads?

Answer 8

• They are expensive.
• They do not understand application behavior.

Question 9

What is multiplexing?

Answer 9

Many-to-Many Implementation

Question 10

What thread offers good perfomance, but does not handle I/O well?

Answer 10

User Level

Question 11

True or False:

Threads are needed for parallel applications.

Answer 11

True

Question 12

What notifies user level schedulers of changes in kernel scheduling decisions?

Answer 12

Scheduler Activations

Question 13

What are the uses for scheduler activations?

Answer 13

• Provides kernel space for threads that block in the kernel.
• Creates one activation for each virtual processor
• Uses upcall to notify kernel of scheduling events.